In spite of insulin therapy, evidence suggests that the insulin-dependent diabetic has an abnormal protein turnover in heart and skeletal muscle resulting in alterations in enzyme formation and abnormal carbohydrate, fat, and protein metabolism. As a result, plasma clearance of triglycerides is diminished, inducing a state of hyper triglyceridemia. It is generally agreed that the excessive quantities of triglycerides and other lipid fractions in plasma of diabetics are, in part, responsible for the fact that they are twice as prone to heart disease as the general population. Previous research with rodents and humans has shown that chronic exercise results in significant increases in the activities of enzymes involved in CHO, fat, and protein metabolism in the trained musculature. Since skeletal muscle represents the major tissue mass of humans, the resulting changes in lipid clearance from plasma and its subsequent oxidation in muscle with training may normalize the plasma triglyceride level in diabetic patients. Unfortunately, there is no information available to describe these training-induced alterations in lipid uptake and utilization in human diabetics. Thus, the purpose of this research will be to study the effects of training on: (1) plasma lipid levels in diabetic patients, (2) mitochondrial enzyme activities in diabetics, (3) lipoprotein lipase activity in diabetics, (4) carbohydrate and lipid metabolism during prolonged exercise in diabetics, and (5) in vitro changes in the oxidative metabolism of CHO (pyruvate) and lipids (14C-palmitate) in skeletal muscle of trained and untrained diabetic patients. Regular endurance exercise coupled with insulin therapy may provide a more satisfactory aternative to current management of the diabetic patient.